Wire Ampacity Chart

TradeHub Tools Field Reference

Primary field chart

Use this chart as a baseline ampacity lookup for common copper and aluminum conductors. The values are field-reference starting points only and do not replace the adopted NEC, conductor markings, terminal ratings, equipment instructions, derating rules, or local inspection authority.

Run the Ampacity Calc

Conductor Size	Copper 60°C	Copper 75°C	Copper 90°C	Aluminum 60°C	Aluminum 75°C	Aluminum 90°C	Field Note
#14 AWG	15	20	25	—	—	—	Small conductor limits usually control.
#12 AWG	20	25	30	—	—	—	Small conductor limits usually control.
#10 AWG	30	35	40	25	30	35	Confirm material, terminals, and OCPD.
#8 AWG	40	50	55	35	40	45	Common branch/feeder starting point.
#6 AWG	55	65	75	40	50	55	Check terminals before using higher values.
#4 AWG	70	85	95	55	65	75	Derating may change usable ampacity.
#3 AWG	85	100	115	65	75	85	Confirm material and terminals.
#2 AWG	95	115	130	75	90	100	Check before derating and voltage drop.
#1 AWG	110	130	150	85	100	115	Verify equipment terminals and wiring method.
1/0 AWG	125	150	170	100	120	135	Service/feeders may add limits.
2/0 AWG	145	175	195	115	135	150	Check sets, terminals, and OCPD.
3/0 AWG	165	200	225	130	155	175	Review service/feeders and equipment.
4/0 AWG	195	230	260	150	180	205	Large conductors need field review.
250 kcmil	215	255	290	170	205	230	Confirm raceway, sets, derating, and terminations.
300 kcmil	240	285	320	195	230	260	Confirm terminations and AHJ conditions.
350 kcmil	260	310	350	210	250	280	Review sets and equipment.
400 kcmil	280	335	380	225	270	305	Check terminals and derating.
500 kcmil	320	380	430	260	310	350	Equipment and AHJ requirements may control.

This chart is a baseline wire ampacity lookup only. It does not approve final wire sizing, terminal temperature use, conductor-count adjustment, ambient correction, NM cable limitations, voltage drop, service conductor sizing, OCPD sizing, or equipment maximum ampacity limits.

Wire ampacity chart showing NEC 310.16 copper and aluminum conductor ampacity reference values — Visual wire ampacity chart for common copper and aluminum conductor amperage lookup under NEC 310.16. Use the calculator for terminal temperature, conductor count, ambient correction, insulation, wiring method, service, and equipment checks.

When This Chart Applies

Use this chart when you need a quick field reference for common copper and aluminum conductor ampacity values before running a full conductor check. It is most useful when the conductor material, size, and insulation-temperature basis are known and the job condition has not yet introduced derating, terminal, equipment, or wiring-method limits.

Material Known

Copper and aluminum values are separated because the same wire size does not carry the same ampacity across materials.

Column Basis Known

60°C, 75°C, and 90°C columns have different uses. Final usable ampacity may still be capped by terminal temperature.

Baseline Lookup Only

The chart is a starting point. Field conditions can lower or change the usable ampacity before the conductor is approved.

Use the Calculator When Conditions Stack

A chart can show a starting ampacity value, but it cannot verify terminal temperature limits, conductor-count adjustment, ambient correction, NM cable limits, service-conductor rules, voltage-drop effects, equipment instructions, or final OCPD coordination.

Ampacity Calculator

Use when THHN/THWN-2 insulation, aluminum conductors, terminal temperature, conductor-count derating, ambient correction, or service/feeders affect usable ampacity.

Wire Size Calculator

Use when load amps, breaker size, conductor material, voltage drop, or workflow handoff affects conductor selection.

Common Field Misses

Using the 90°C column as a final ampacity instead of treating it as an adjustment or correction basis where permitted.
Ignoring 60°C or 75°C terminal temperature limits on equipment terminations.
Forgetting current-carrying conductor adjustment when multiple conductors share the same raceway or cable.
Treating voltage drop, OCPD sizing, or equipment maximum ratings as if they were approved by the ampacity table alone.

Related code references

Related NEC Field References

NEC 310.16 Ampacity Table Source scope for conductor ampacity lookup. NEC 110.14(C) Terminal Temperature Terminal limits can cap the final usable ampacity. NEC 310.15 Adjustment and Correction Conductor count and ambient temperature can reduce ampacity. NEC 334.80 NM Cable Ampacity Cable assembly limits can change how ampacity is applied.

Source Alignment and Use Scope

This field chart is a quick-reference summary used to support TradeHub calculator workflows and common NEC 310.16 ampacity lookup. It is for screening and planning only and does not reproduce the complete adopted NEC table, approve a final conductor selection, or replace local amendments, manufacturer instructions, plan review, utility requirements, or AHJ interpretation. Review the TradeHub Code Citation & Source Log for source alignment records and the TradeHub Methodology page for how field references are scoped.

Wire Ampacity FAQ

Is a wire ampacity chart the same as a final wire size calculation?

No. A wire ampacity chart is a baseline conductor ampacity lookup. Final conductor selection can also require terminal temperature limits, conductor-count adjustment, ambient temperature correction, wiring method limits, equipment instructions, voltage drop, and overcurrent protection review.

Can I use the 90 degree ampacity column as the final ampacity?

Not by itself. A higher insulation-temperature column may be used for adjustment or correction only when permitted, but the final usable ampacity still cannot exceed the applicable terminal temperature limit.

Why does the same wire size show different amp ratings?

The ampacity depends on conductor material, insulation temperature rating, terminal temperature limits, ambient conditions, number of current-carrying conductors, and wiring method. That is why the chart is only a starting point.